The present invention relates to a two-cycle engine that achieves improved fuel economy due to the addition of a ceramic element formed in the wall of the head of the cylinder facing the combustion chamber.
It is conventionally known to use heat-insulating ceramic elements in all or some of the components that make up the combustion chamber of an engine such as the head of the cylinder, the cylinder block and the piston. The advantage of using ceramic elements is particularly great in diesel engines because such use increases the thermal efficiency and reduces the fuel consumption, particularly, achieving a more effective burning of low-grade fuels. However, if ceramic elements are used to form the combustion chamber of a four-cycle engine, little increase is attained in the power output, and instead, the temperature in the combustion chamber is increased to such an extent that knocking or preignition occurs easily.
The present inventors previously found that the performance of a two-cycle engine could be increased by forming the head of the cylinder with a heat-insulating ceramic material such as silicon nitride, zirconia or sialon. The ceramic material helps increase the temperature of the wall of the cylinder head facing the combustion chamber, promoting the evaporation into finer particles of the fuel in the intake air-fuel mixture and residual or burnt gas. As a result, a higher power output is attained from the engine while providing a greatly reduced fuel consumption. However, as the temperature in the combustion chamber is increased, the temperature of the spark plug also increases and hence knocking or preignition can occur easily.